Various devices for forming fluid cushions or fluid bearings have been proposed for the contactless support of a web as the latter changes directions during its course of travel. These webs may have printed matter on both sides and which must be dried without contact of the web by any supporting rollers or the like. These running webs to be dried must pass through a number of runs of different directions and the web must be held out of contact with anything until the ink has dried. These contactless supporting devices have a generally partially cylindrical surface through which pressurized air is introduced through various slots, holes, or apertures, or other designs or patterns.
Examples of such prior art devices are shown in the Daniels U.S. Pat. No. 2,689,196 which issued Sept. 14, 1954 wherein a series of holes are simply formed in the cylindrical surface for the passage of pressurized air therethrough to support and guide a web passing over the drum. Another example is shown in the U.S. Pat. No. 3,097,971 to Carlisle which issued July 16, 1963 and which has a series of slits in the curved supporting surface and which extend either longitudinally or transversely to the web, or both. Air under pressure is then passed through these slits to form a cushion between the drum and the web. Still another example is shown in the U.S. Pat. No. 3,567,093 which issued Mar. 2, 1971 to Johnson and wherein a series of holes is formed in the drum-like supporting member and a series of arcuate baffle members extend around a portion of the drum and in the direction of web movement. Still other examples of the prior art are shown in U.S. Pat. No. 3,127,080 issued Mar. 31, 1964 to Allander et al and U.S. Pat. No. 3,186,326 which issued June 1, 1965 to Schmidt and in both of the latter patents, air is passed through slots of holes in the cylindrical members to form a pressurized cushion between the cylindrical member and the web.
One shortcoming of the prior art devices of the general type to which this invention pertains is the fact that the cushion of air between the web and the drum is dissipated, usually along the opposite edges of the web or the pressure cushion is otherwise not maintained uniform across the width of the web and particularly at the edges of the web where the pressure tends to fall off to an extent that the web edges are not adequately supported. Another problem of the prior art devices is that excessive horsepower was required to provide the necessary air flow and excessive air flow was required for adequate contactless support of the web during operation.